textproduct: Albany

WHAT HAS CHANGED

Models have come into decent agreement that the heaviest rainfall totals on Sunday night into Monday will be focused across far northwestern areas (western Adirondacks) and southern/southeastern areas (Catskills, mid Hudson Valley and western New England), with maximum amounts around two inches possible. Areas that saw heavy rainfall earlier in the week area most at risk for additional flooding concerns.

KEY MESSAGES

1) A slow moving cold front will result in periods of showers and thunderstorms across the entire region for Sunday night into Monday. With bursts of heavy rainfall expected, there will be the potential for isolated to scattered flash flooding, with areas that saw high rainfall amounts earlier in the week most susceptible to renewed flooding.

DISCUSSION

KEY MESSAGE 1...

A cold front and associated upper level trough will be very slowly moving eastward from the Great Lakes and into the Northeast for Sunday into Monday. Ahead of this boundary, it will be very moist across the region, with surface dewpoints well into the 60s, with some low 70s in valley areas. PWAT values will be exceeding two inches in many areas by early Monday and these values are 2-3 STD above normal. Guidance suggests rounds of showers and embedded thunderstorms will start impacting northwestern areas by later Sunday, with the highest coverage across the area for Sunday night through Monday afternoon.

Model soundings shows a low of ingredients that would favor the potential for heavy downpours and possible flash flooding. In addition to the high PWATs, there will be a moist profile throughout the entire troposphere, high freezing levels and a narrow skinny CAPE profile. This would result in highly efficient rainfall processes, allowing for heavy downpours.

There has been some question about where the heaviest rainfall will set up and some of the guidance has helped put this into better focus. Based on the latest info, northwestern areas (western Adirondacks) may see some of the heaviest downpours initially for late Sunday into Sunday night. For Monday, it appears far southern and southeastern areas may be most at risk, with the heaviest totals perhaps just south of the area into the northern mid Atlantic States. While the NBM suggests that there is a decent chance for a widespread 1" of rainfall (over 50 percent for many areas), it is not showing too high potential for over 2" (with under 20% for most of the region). Still, hi- res guidance, including the 12z SPC HREF, does suggest the potential for locally 2-3" in some areas that see repeated bursts of heavy rainfall for western and southern areas. The areas most at risk will be locations that saw heavy rainfall earlier in the week, as soils remain saturated and FFG is rather low for these areas. While far southern areas (such as near Poughkeepsie) are still in a rainfall deficit, locations not far away across northern parts of the mid Hudson Vally are fairly wet, so will need to closely monitor radar trends Sunday into Monday once showers and thunderstorms develop. There is currently a marginal risk for flash flooding for Sunday night into Monday for most of the area. Far southern areas (Dutchess and Litchfield Counties) also reach into the Slight Risk, which suggests the potential for isolated to scattered flash flooding.

Showers and thunderstorms will be winding down by Monday evening, as the best forcing and moisture shifts eastward, which will end the potential for any additional flooding by that time.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Through 18z/Sunday...VFR conditions prevail through most of the TAF period. Scattered to broken fair weather cumulus and cirrus pass through this afternoon with increasing coverage into the evening. Model soundings suggest there is the potential again for patchy fog/mist to develop across some of the terminals near sunrise tomorrow with sufficient moisture and light winds in place. Flight conditions could lower to MVFR/IFR with periods of LIFR possible with the best chances at KGFL and KPSF, however the chance is also mentioned at KALB and KPOU. Cloud cover could limit this potential so confidence will increase with the next TAF cycle. Low stratus is expected after sunrise tomorrow morning through about mid morning ahead of an approaching frontal system but should remain VFR. Winds this afternoon will be out of the south/southeast at KGFL and KALB and out of the southwest at KPOU and KPSF with speeds 5-10 kt and an occasional gust up to 15 kt. Winds this evening become light and/or calm generally 5 kt or less except for at KALB where winds hold near 5-8 kt before increasing by morning across all terminals out of the southeast to 10-15 kt and gusts 20-25 kt.

Outlook...

Sunday Night: High Operational Impact. Definite SHRA...TSRA. Monday: High Operational Impact. Likely SHRA...TSRA. Monday Night: Low Operational Impact. Slight Chance of SHRA. Tuesday: Low Operational Impact. Slight Chance of SHRA. Tuesday Night: Low Operational Impact. Slight Chance of SHRA. Wednesday: Moderate Operational Impact. Chance of SHRA...TSRA. Wednesday Night: Moderate Operational Impact. Likely SHRA...TSRA. Thursday: High Operational Impact. Likely SHRA...TSRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.